Following our HEALTHbeat issues on the above topics, we received a number of insightful questions from our readers. We enlisted the help of Caitlin Hosmer Kirby, a senior nutritionist at Harvard-affiliated Brigham and Women's Hospital to help answer them.

Are the relatively recent “fat free” half-and-half products good for you?

Consider them good in the way that diet soda is good—because of what you are not having. These are synthetic products manufactured to give you the mouthfeel (consistency) and taste of a food high in unhealthy saturated fats. If used in moderation to allow you to enjoy some heavy foods in a lighter form, they can be helpful. But these products in and of themselves don’t enhance your diet, and they can give a false sense of security as far as calories are concerned—people often end up consuming a lot of calories from these fat-free foods. Depending on your health status, keeping small amounts of "real" half and half as part of your diet is fine, as long as it's done in moderation.

In your article on butter vs. margarine, you didn’t mention Smart Balance as a choice for a sterol spread. Why not?

Smart Balance can be added to the group of good products available to those looking to control risk factors for cardiovascular disease. In fact, the original Smart Balance offers the advantage of being a vegetable oil-based omega-3 spread that is free of trans fats, which is not true of all spreads. But the original Smart Balance spread doesn't contain plant sterols and therefore didn't make our list of plant sterol products. Recently Smart Balance has branched into products that contain both omega-3 fats, which provide a variety of health benefits, and plant sterols, which can help lower cholesterol.

What are the benefits of taking flaxseed? Is it better to include flaxseed oil or the actual flax seed in my diet?

Flaxseed and flaxseed oil are both high-quality sources of healthy omega-3 fats, with slightly different characteristics. They are both a good option for people who don't like fish or fish oil supplements. Flaxseed oil is a more concentrated source of omega-3 fats than flax seeds, but contains only the alpha-linolenic acid component of flaxseed, and not the fiber or lignan components contained in the seeds themselves (though some oils have lignans as well). Therefore, flaxseed oil may share the heart-healthy properties of flaxseed, but not the additional fiber and anti-cancer benefits provided by the actual seeds. Flax seeds may have a slight leg up on flaxseed oil, overall, but remember that the seeds must be ground in order for your body to reap the health benefits.

Are there other food sources or products that provide omega-3 fatty acids?

There are two families of omega-3 fats: the plant-derived alpha-linolenic acid (or ALA) and the "marine" omega-3 fats, EPA and DHA, which come mostly from seafood. Flax seeds and flaxseed oil are the best source of plant-derived ALA, but there are other sources. These include walnuts, tofu and other forms of soy, as well as vegetable oils such as canola or walnut. There are also new products (spreads or peanut butters) that have added flaxseed oil. EPA and DHA are found only in fish oil and to some degree in omega-3 enriched eggs (egg-laying hens are fed omega-3 enriched feed). There is some debate as to whether ALA offers the same cardiovascular benefits as EPA and DHA, but while we wait for an answer, the ALA-rich foods mentioned above remain good choices to be part of a healthy diet.

Isn't there new evidence that possibly links increased ALA intake to prostate cancer?   How can I protect myself against prostate problems?

Diet does appear to have an important influence on a man’s risk of prostate cancer. Saturated fats, particularly those from red meat and whole dairy products, are linked to an increased risk, and they are bad news for general health as well. But a few items typically considered healthful have been associated with an elevated risk of prostate cancer. They include a very high consumption of calcium and, as you mention, alpha-linolenic acid, the omega-3 fatty acid in flaxseed and canola oil. It’s wise for men to keep their saturated fat consumption down to less than 10% of their total calories, to limit calcium to less than 1,500 mg a day, and to count on fish or fish oil rather than ALA for heart-healthy omega-3s. And men should get lots of whole grains, tomatoes (especially cooked tomatoes), other fruits and vegetables, fish, and soy products, all of which have been associated with a reduced risk of prostate cancer and many other woes.

Is it inadvisable to use plant stanol/sterol margarines because of the trans fats?

It is true that some margarines containing plant stanols and/or sterols also contain a small amount of trans fats (0.1–1 grams per tablespoon). It is also true that, while there is no “recommended” minimum level of trans fat, you want to keep your intake as low as possible. It’s hard to say whether the trans fat in these spreads negates the cholesterol-lowering benefits of sterols and stanols. Companies will continue to formulate new products, though, so be on the lookout for products without trans fats.

Your issue about the benefits of eating breakfast stated that eggs are best left to “the occasional brunch.” The previous issue stated that eggs are probably not as unhealthy as once thought. Isn’t this contradictory?

For the most part, no single food is good or bad. While it is true that eggs are not the dietary demons once believed, eating eggs for breakfast regularly means that you’re missing out on the benefits of a whole-grain, high-fiber breakfast cereal. Balance truly is the key to healthy eating.

In the question and answer on flax seed, the table referred to there being 6.2 grams of the compounds in a tablespoon, which carries 120 calories, while the answer to the question referred to 6.2 grams of the compounds in a teaspoon. Can you please clarify?

The problem here is that we're talking about two distinct types of flaxseed oil. There are 6.2 grams of omega-3 fats in one teaspoon of a concentrated flaxseed oil supplement. The question and answer was referring to plain flaxseed oil, which contains 120 calories in a tablespoon. Remember that plain flaxseed oil contains other types of fats in addition to omega-3s, so on the label you might notice that there are more total calories than calories just from omega-3 fat.

Do stanol spreads lower good HDL cholesterol?

The literature on stanols mostly notes their beneficial effects on total cholesterol and LDL. A summary paper published in the Journal of Nutrition reports that most studies have not shown a significant effect on HDL cholesterol or triglycerides.